Creep behaviour of porous metal supports for solid oxide fuel cells

The creep behaviour of porous iron-chromium alloy used as solid oxide fuel cell support was investigated, and the creep parameters are compared with those of dense strips of similar composition under different testing conditions. The creep parameters were determined using a thermo-mechanical analyser with applied stresses in the range from 1 to 15 MPa and temperatures between 650 and 800 °C. The Gibson-Ashby and Mueller models developed for uniaxial creep of open-cell foams were used to analyse the results. The influence of scale formation on creep behaviour was assessed by comparing the creep data for the samples tested in reducing and oxidising atmospheres. The influence of pre-oxidation on creep behaviour was also investigated. In-situ oxidation during creep experiments increases the strain rate while pre-oxidation of samples reduces it. Debonding of scales at high stress regime plays a significant role affecting the creep behaviour of the metal supports, in particular the stress exponent. The variation of the elastic modulus as function of temperature and oxidation conditions was also determined by a high temperature impulse excitation technique. Additionally nano-indentation testing was performed in the metal oxide interface to elucidate the mechanical properties of the oxide scales and qualitative information about the oxide scale-metal interfacial bonding.